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The Effects of Magnesium, Zinc and Calcium Ions on Endotoxin-Plasmid DNA Interaction at Various Cation Concentrations, pH Values and Incubation Times
  • Clarence Ongkudon,
  • Elvina Clarie Dullah,
  • nur Syahadatain Abdul Razak
Clarence Ongkudon
University Malaysia Sabah

Corresponding Author:[email protected]

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Elvina Clarie Dullah
Universiti Malaysia Sabah
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nur Syahadatain Abdul Razak
Universiti Malaysia Sabah
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In plasmid DNA (pDNA) production from Gram-negative bacteria, endotoxin has been known as the major contaminant. The separation becomes difficult due to its ability to form a stable complex with pDNA apart from sharing common properties like surface charge, molecular size, temperature and pH stability. This study focused on the analysis of zeta potential of endotoxin, theoretical number of cation bound per molecule of endotoxin as well as binding tendency of cations towards endotoxin in the presence of pDNA. These analyses were conducted under various experimental conditions such as types of divalent metal cation, cation concentration, pH and incubation time. The analysis of zeta potential at different cation concentrations and pH values showed that Mg2+ had the most significant effect on endotoxin surface charge. The zeta potential of endotoxin reduced by a magnitude of 43.55 mV, from -43.53 mV to 0.02 mV in the presence of 2.0 M Mg2+, and a magnitude of 44.12 mV , from -43.53 mV to 0.59 mV at the lowest pH level. However, in the analysis of theoretical number of cation bound per molecule of endotoxin, Zn2+ showed the highest number (0.6) compared to Ca2+ (0.12) and Mg2+ (0.05). The tendency of Zn2+ to preferentially bind with endotoxins forming larger aggregated structure was also evident in the DNA gel electrophoresis and transmission electron microscopic analysis.